1. Field of the Invention
This invention relates to single phase motors having an auxiliary or start winding and a main winding.
2. Brief Description of the Prior Art
Air conditioning apparatus include hermetically sealed compressors typically powered by single phase electric motors. The motors are disposed within the compressor shell and electrically energized through pins mounted to extend through a glass header placed in the wall of the compressor shell. The motors are generally provided with a winding circuit which includes a main winding and an auxiliary or start winding connected in parallel with the main winding. During motor starting and running both the main winding and the start winding are connected across the motor power source to magnetically excite the rotor and cause rotation thereof.
It is conventional to place a capacitor in series with the start winding to alter the phase angle and achieve desired starting torque and running efficiency. The capacitor is connected outside the compressor shell to appropriate pins.
Although it is known to place a motor protector within the compressor shell, which provides certain advantages, such as being more responsive to motor winding temperature, it is most frequently preferred to place the protector outside the compressor shell, electrically interposing it between one line and the common pin because it is less expensive, and doing so facilitates field servicing.
A typical room air conditioning compressor is provided with a glass header arrangement as shown in FIG. 1 having three electrical terminal pins, start, main and common equidistantly spaced from one another. Male spade connectors are welded to the pins to facilitate connection to wire leads by conventional female flag quick connectors as shown in FIG. 2.
This arrangement, while being conducive to easy assembly, permits placement of wire leads on the terminal pins in an incorrect sequence which can result in malfunction of the motor. Improper wiring connections are very undesirable, particularly with rotary compressors.
It is an object of the present invention to provide structure which prevents miswiring. Another object of the invention is the provision of a simple, inexpensive yet reliable apparatus which will ensure that correct wiring connections are made to the electrical terminal pins of a compressor motor. Another object is the provision of a motor protector particularly adapted to prevent miswiring, one which is easily calibratable and one which is fail safe in operation.
Briefly, in accordance with the invention, in a first embodiment a keyed plug on motor protector is received on the common terminal pin, with the motor protector housing occupying the majority of the space which the pins define. First and second right angle female flag quick connectors, being mirror images of one another, to provide polarized or right and left hand orientations are then used to connect to the start and main terminal pins with the first connector receivable on only one of the start and main terminal pins and the second connector receivable on only the other of the start and main terminal pins.
The motor protector is provided with a female quick connector having a size selected so that it is receivable only on the spade terminal welded to the common pin. The spade terminal is chosen to be slightly smaller than the spade terminals welded to the main and start pins. The female quick connector of the motor protector, according to a feature of the invention, has an arm which, using a solder which melts at a selected temperature, is soldered to a support member which mounts an end of a current carrying thermostat member. The arm is adapted to spring away from the support member and interrupt the circuit in the event that a selected overtemperature occurs, thereby melting the solder. Calibration of the opening temperature of the motor protector is provided by a calibration screw aligned with a selected portion of the thermostat member.
In a second embodiment of the invention a pair of protrusions are formed on the motor protector housing adapted to project toward the main and start pins when the motor protector is mounted on its blade terminal in order to prevent placement of polarized female quick connectors on improper pins.